Department of Electrical and Computer Engineering, University of Houston, Houston, Texas.
Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland.
Magn Reson Med. 2020 Mar;83(3):1055-1065. doi: 10.1002/mrm.27963. Epub 2019 Aug 29.
The paper investigates factors that affect the RF-induced heating for commonly used wire-based sternal closure under 1.5 T and 3 T MRI systems and clarifies the heating mechanisms.
Numerical simulations based on the finite-difference time-domain method and experimental measurements in ASTM (American Society for Testing and Materials) phantom were used in the study. Various configurations of the wire-based sternal closure in the phantom were studied based on parameter sweeps to understand key factors related to the RF-induced heating. In vivo simulations were further performed to explore the RF-induced heating in computational human phantoms for clinically relevant scenarios.
The wire-based sternal closure can lead to peak 1-g averaged spatial absorption ratio of 106.3 W/kg and 75.2 W/kg in phantom and peak 1-g averaged specific absorption rate of 32.1 W/kg and 62.1 W/kg in computational human models near the device at 1.5 T and 3 T, respectively. In phantom, the simulated maximum temperature rises for 15-minute RF exposure are 9.4°C at 1.5 T and 5.8°C at 3 T. Generally, the RF-induced heating will be higher when the electrical length of the device is close to the resonant length or when multiple components are spaced closely along the longitudinal direction.
The RF-induced heating related to wire-based sternal closure can be significant due to the antenna effect and capacitive mutual coupling effect related to the specific geometries of devices.
本文研究了在 1.5T 和 3T MRI 系统下，常见的基于金属丝的胸骨闭合装置在射频（RF）激励下产生的加热效应的影响因素，并阐明了其加热机制。
本研究采用基于时域有限差分法的数值模拟和 ASTM （美国材料与试验协会）体模中的实验测量。通过参数扫描研究了体模中基于金属丝的胸骨闭合装置的各种配置，以了解与 RF 诱导加热相关的关键因素。进一步在计算人体模型中进行了体内模拟，以探索临床相关场景下的 RF 诱导加热。
基于金属丝的胸骨闭合装置在 1.5T 和 3T 时，在装置附近的峰值 1g 平均空间吸收率分别为 106.3 W/kg 和 75.2 W/kg，峰值 1g 平均比吸收率分别为 32.1 W/kg 和 62.1 W/kg。在体模中，15 分钟 RF 辐射的模拟最大温升为 1.5T 时 9.4°C，3T 时 5.8°C。一般来说，当装置的电气长度接近谐振长度或多个组件沿纵向紧密间隔时，RF 诱导加热会更高。
由于装置的特定几何形状引起的天线效应和容性互耦效应，基于金属丝的胸骨闭合装置的 RF 诱导加热可能会很显著。
